The use of terpenes as odorants is known in the art. GB425309, for instance, describes that air in closed spaces, such as theatres, is purified by vaporizing therein a mixture of camphene with menthol and with one or more other terpenes such as pinene and phellandrene, and with or without alcohol. Mixtures specified are (1) menthol and oil of camphor, and (2) menthol, oil of camphor and alcohol. The vapors are introduced into the air at a point where there is an undisturbed upward flow of warm air. Perfumes may be added to the purifying agents.